1. Field of the Invention
This invention relates to tube protection devices and methods. More particularly, the present invention relates to devices and methods to protect vacuum tubes, such as diffusion furnace tubes used in semiconductor manufacturing equipment, during their installation in and removal from diffusion furnaces, and the like.
2. Description of the Related Art
Conventionally, diffusion furnace vacuum tubes are installed by sliding the unprotected tube through a particulate laden vestibule block and onto and through the heating elements of the furnace, and then though another vestibule block. However, as the tube is slid through the vestibule blocks of the furnace, the edge of the tube tends to shave particles off the blocks, which particles collect within and around the vacuum tube. As the vacuum tube must be maintained in as pristine a state as possible during installation, the particles shaved from the vestibule blocks necessarily degrade the performance of the tube.
However, the vestibule blocks are not the only source of undesirable particulate matter within and around the tubes. Indeed, the heating elements of the diffusion furnace are also a contaminant source. The heating element coils of the diffusion furnace are separated by insulators. Once the tube has been inserted through the first vestibule block, it must slide past the heating element coils. As the tube is slid through the heating element coils of the furnace, its sealing surface is pushed, shoved, dragged and scrapped across the insulators of the heating elements. This pushing, shoving, dragging and scrapping across the insulators of the heating elements scratches and may actually chip the vacuum tube. Such scratches and chips may and often do cause undesirable vacuum leaks.
Therefore, the tube accumulates particles and other contaminants as it passes through the first vestibule block, may acquire scrapes or chips as it is dragged past the heating coil insulators, and accumulates additional contaminants and particulate matter as it is slid past the second vestibule block. Such scratches, chips and particle contamination degrade the performance of the tube, and cause vacuum leaks. When such contamination or damage to the tube occurs, the tube must be removed, cleaned and repaired, if possible. Such damage may lead to failed product runs, costly down time and the immobilization of a furnace or production line until a replacement tube can be found and installed without excessive damage thereto.
When the tube is removed from the diffusion furnace, the above-described steps are performed in reverse order. However, since the tube is now pulled back through the second vestibule block, the tube occasionally slips out too quickly and drops onto the heating element. As the vestibule's internal diameter is smaller than the internal diameter of the heating elements, they are now on the same plane. Such a drop may, and frequently does, result in a broken tube. Such broken tubes must thereafter be replaced, again immobilizing the furnace, and possibly the entire line until a replacement tube can be located and installed. Moreover, such tubes are costly to replace, both in terms of the value of the tube itself as well as in terms of unproductive down time.
There has been a long felt need, therefore, for devices and methods of protecting such tubes during insertion into and withdrawal from furnaces. In particular, what is needed is a device and a method to prevent particulate matter from contaminating interior and exterior surfaces of such tubes during installation. What is also needed is a device and a method to prevent such tubes from becoming scratched and chipped as they are inserted through and removed from the furnace, past the heating and other internal elements of the furnace.